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I can't find that passage, but I remember someone (can't remember who) in one of the books (can't remember which one!) says that even though Muggles can't see them, they can still feel their presence. Also, Dudley did say that he remembered things when he encountered them, and judging by the state he was left in, he did feel that they were there.

I thought it was very clear that Muggles could sense the presence of a dementor. Dudley definitely felt it, that's not up to debate. He described what he felt to his parents all on his own, except when he got to the point where he simply couldn't say anything more and Harry finished for him, with "As if you'd never be happy again." Dudley then confirmed that that was how he felt. Then in Half-Blood Prince there's this bit:

"'A grim mood has gripped the country,' the [Prime Minister's] opponent had concluded, barely concealing his own broad grin.

And unfortunately, this was perfectly true. The Prime Minister felt it himself; people really did seem more miserable than usual. Even the weather was dismal; all this chilly mist in the middle of July....It wasn't right, it wasn't normal..."

All that misery and mist? That's dementors. Fudge says later in the chapter, "That's what's causing all this mist." So it's clear, not only from Order of the Phoenix, but Half-Blood Prince as well, that Muggles, while wholly non-magical, can sense dementors.

Edit: I found another passage where is says Muggles can feel the presence of Dementors. In Prisoner of Azkaban, page 187 (US Hardcover ed.) Lupin says "Even Muggles feel their presence, though they can't see them." That must be the passage you were remembering, Sapphire at Dawn.

Thinking about wizarding genetics makes my head hurt and I generally avoid it, but I'm curious to see what people think about the possibility of magical ability being diluted by Muggle blood.

I'd like to think not, of course, since (a) JKR has clearly made a point of showing that blood/family does not determine magical ability/personal worth, (b) it would justify some of the pureblood sentiments, and (c) it's just mean, but it would help explain why wizards are such a tiny minority of the population.

I was actually thinking about it with regards to the "Wizards and New World Natives" thread, but I think it fits better here. To explain what I mean, though, I was thinking that Native Americans probably did not always distinguish properly between wizards and Muggles - i.e. they sometimes attributed magical powers to Muggles, and sometimes did not notice that wizards had special powers. Given that, it seems highly unlikely that Indian wizards would have worried about "maintaining pure blood lines" or any of that, and if wizards are really so rare, Indian wizards probably married Muggles nearly every time. So why wouldn't there be huge numbers of half-blood Indian wizards (which I suppose arguably there might have been, but it doesn't seem plausible if HP canon includes the basic points of our own history)?

Anyway, I'd always figured that magical ability was directly tied towards intelligence - Dumbledore would've been a brilliant person Muggle or wizard; since he had magic, he was therefore also an extremely powerful wizard; Crabbe and Goyle were idiots, and therefore also poor at magic. But perhaps if say, a pureblood wizard marries a Muggle, and their child also marries a Muggle, and so on down the line, after a few generations one of these technically half-blood offspring would be a squib, or someone with weak enough magic to preclude acceptance into a wizarding school. Maybe if that person was a bit stupid, too? So Crabbe and Goyle only got the magic gene because they're pureblood, but a half-blood of equal intelligence would've been a squib/Muggle/whatever. And then he/she might have a very bright great-great-grand-child down the line who popped up as a Muggle-born. But then that would mean the majority of Muggle-borns are of above-average intelligence, which seems sort of unfair...

This is the problem; every explanation I come up with to explain why the HP world is not overrun with wizards falls apart at the least provocation. I rather like the idea of people walking around with weak magic, though, perhaps developing weird little supernatural abilities like the ability to heal bruises or make crops grow faster or something.

Well, if anyone finds anything the least bit sensible/useful in this post, kindly share your thoughts, because this is really bothering me now.

To explain what I mean, though, I was thinking that Native Americans probably did not always distinguish properly between wizards and Muggles - i.e. they sometimes attributed magical powers to Muggles, and sometimes did not notice that wizards had special powers. Given that, it seems highly unlikely that Indian wizards would have worried about "maintaining pure blood lines" or any of that, and if wizards are really so rare, Indian wizards probably married Muggles nearly every time. So why wouldn't there be huge numbers of half-blood Indian wizards (which I suppose arguably there might have been, but it doesn't seem plausible if HP canon includes the basic points of our own history)?

Well, a few things. First, most of us operate under the presumption that half-wizarding, half-Muggle children are going to be wizards and witches. It's quite possible that the children of a witch and a Muggle (e.g.) would have fifty-fifty chances of inheriting magic, or only twenty five percent chance of inheriting magic, if the genes work recessively.

Second, why would Native Americans be unaware of what magic meant? Just because they do not have a history of discriminating against witches doesn't mean that they wouldn't be able to figure out when someone can do things like not be injured when they're dropped out a window (see: Neville)

Third, even if magic was not treated as unusual, witches and wizards would still probably want to marry each other. Why? Because that will increase the probability that their children will also be witches and wizards. Basic genetics.

As for magic being diluted by Muggle blood, wouldn't that make Muggle born witches and wizards inherently weaker? Hermoine Granger is pointedly a brilliant witch, though she works at it extremely hard.

I think it's more likely that skill at magic is like skill in anything else. There's what you were given genetically and there's how hard you work at it. You may be born with more inherent power, but if you don't work at it, you won't be any better.

I just keep thinking back to Ron's little speech in CoS about all wizards having at least some Muggle ancestory, and how if they hadn't married Muggles, wizards everywhere would have died out.

I feel like this statement implies that the chances of having a wizarding child with a Muggle would be very good, suggesting some sort of dominant gene. We all know how different Muggle society is from wizarding society and all the problems that could likely surface in a mixed marriage. I feel like when it would come to marrying Muggles for the sake of the population, there would having to be a very good chance of giving birth to a magical child. Otherwise, if the marriage was for the sake of keeping the wizarding population, I feel like it would be a very poor plan if having a wizarding child came down to little more than a crapshoot.

Another thing I just have to think Would be that a true wizard and a Muggle would have to have a higher chance of having a magical child than two Muggles carriers or a Muggle carrier and a Squib. If magic is a dormant carrier gene in each of the parents, than the child would have a one in four chance of being born with magic (much the same way cystic fibrosis works), making the exact term for it an autosomal recessive pattern. Though neither parent is capable of using magic themselves, because of this gene, they are capable of having a wizarding child together. But, if a carrier were to have a child with a parent who is not a carrier, they child would be a Muggle, but would still be a carrier.

Also, as far as the blue eyes recessive gene, a person who does have blue eyes would be as follows: bb; while someone who is only a carrier for the blue eye gene would be Bb. If magic followed this pattern, that would mean for a wizard to have a wizarding child with a Muggle, the Muggle would have to be a carrier themselves, and then they would have a one in two chance of having a magical child as opposed to the one in four of two Muggle carriers.

Then again, I don't see a lot of wizard in much more olden times willing to marry into Muggle families for the sake of their population if all they had was a half and half chance of somehow preserving the wizarding race.

As to the statement about Native Americans, it could be possible that they did not carry the same level of descrimination (wizard vs. Muggles) as the Europeans do, but whether or not they have a higher amount of magical births depends on which theory of wizarding genetics you percribe to.

So it would seem so far we have serveral theories when it comes to magical genetics:

Magic is a dominant gene and one wizarding parent will always have wizarding children.

Magic is a recessive gene and a wizard must of children with a Muggle carrier in order to have a one in two chance of having a wizarding child.

Two Muggle carriers are needed in order to have a one in four chance of having a Muggle-born child.

Magic is most likely a two allele trait (either the child has magic or they don't, there is no real range)

But now, under this thinking I wonder if instead of Squibs being the result of some random defect due to inbreeding, if they are somehow the result of rome random Muggle in their family line, making them a potential carrier, Mm, for a Squib that will resolt if they have child with another Mm carrier.

Then again, this would make Squibs far mote common than canon would dictate (seeing as they are supposed to be far less common than Muggle-borns), and seeing as even they Black family can have Squibs, the idea that they result as a defect from inbreeding is starting to seem more and more likely.

And since we are talking strictly in theory, and there is no chance of being able to perform any experiment to conferm any sort of hypothosis, it would seem that until J.K. writes more books or an encyclopedia, it is all just still going to come down to opinion.

It is actually possible that the wizarding genes are recessive, not dominant. Remember, that Purebloods, Half-bloods and Muggleborns are just terms given according to heritage, not by their genotype. All wizards, (of any blood type), might be of the genotype MM, whereas carrier Muggles (not having magical ability) can be Mm, and just normal Muggles are mm. That actually also explains the ratio of wizards:Muggles- 3:1.

Let’s look at some genetic diagrams (I think they are called Punnet squares, I forgot >.< )

This actually kind of explains Muggle-borns. If they were born to two carrier Muggles, they turn out to be witches or wizards. For example, Lily’s case, if her parents were two carrier Muggles, then she was a witch, whereas Petunia was a Muggle, whether normal or carrier. Personally, I wish she was a carrier, because then there is a chance that Dudley inherits the gene, and if he marries a carrier Muggle, his child can be a wizard/witch (I know, JK squashed that possibility by saying that they would not survive Vernon’s genes, but… whatever, a girl can dream.)

As for Half-bloods, they were possibly born to wizards and carrier Muggles.

And anyways, let’s face it, we don’t even know about all the heritages of every single witch and wizard. We only know about a handful of the population. If the genes were not recessive, then don’t you think that there would be many more witches and wizards roaming around? This theory kind of explains it.

And about Squibs… I think it’s just a mutation. Definition of mutation: a rare, random and spontaneous change in a gene or chromosome. As we know, Squibs are rare. So it is a possibility that some of the genes got tweaked a bit, thus producing squibs.

Or there is another theory. Assume that the parents were a wizard/witch and a carrier Muggle (I know they are born to two magical parents, but hear me out.) But the parent carrier Muggle’s genes mutated, so somehow the recessive gene showed its effect instead of the dominant one, thus making them magical. They would never know if one of their parents were magical already, since they can’t test genetics...... M...MM MM MMm Mm Mm

Explains squibs (the Mms ), But this is just a theory. And maybe that’s why they have SOME characteristics of witches and wizards, because of the M allele.

And you also have to take into account how hard someone tries. Magic is affected my external stimuli as well. E.g., Hermione, though she is a Muggleborn, is such a good witch because she tries so hard. The Kwikspell course helps witches and wizards to be better. Ariana lost her magical powers because of those boys. And Neville, though he is a Pureblood wizard, is so weak, possibly due to the loss of his parents.

^I find myself thinking that the only canon explanation of magical inheritance is that it's wildly complicated, depends on many genes, and is basically so far lodged into the depths of the human genome as to be indecipherable; i.e. maaaagiiiiic!

My major problem is that in terms of natural selection, it doesn't make sense for magic to be limited to such a small portion of the population. Doesnt just being a wizard extends your life in JKR's world, aside from all the advantages a wizard has over a Muggle? That right there should mean that wizards have, since the dawn of man, had more kids and thus should have a greater chunk of the gene pool. And yes, I suppose there are arguments about the power of social norms and humans not being like other animals; we're self-conscious and don't make decisions solely on the basis of breeding etc. etc. I suppose it goes to how far back on the evolutionary tree magic exists - which, given that there are magical animals, is presumably pretty far. Actually, why aren't there more/any primates with magic? But anyway, recessive or dominant, a gene/genes that useful should become the norm. As I recall (and it's been...oh jeez...3? years since AP Bio, so bear with me), the gene for a sixth finger is actually dominant, but since it's not evolutionarily useful, the vast majority of us have the recessive combination.

I just don't see how it could be put into a standard genetic model and yet still be so rare when it is inarguably a good thing, especially as it doesn't seem likely that every wizarding society would have sequestered itself from Muggles the way the English/presumably all the Europeans did. So I think inheriting magic must be terribly complex and mysterious, like the various aspects of intelligence or personality. More than that, there must be something, well, magical, preventing the magic gene from spreading too far into the population (beyond just Squibs, given how rare they are).

Originally Posted by AidaLuthien

As for magic being diluted by Muggle blood, wouldn't that make Muggle born witches and wizards inherently weaker? Hermoine Granger is pointedly a brilliant witch, though she works at it extremely hard.

I think it's more likely that skill at magic is like skill in anything else. There's what you were given genetically and there's how hard you work at it. You may be born with more inherent power, but if you don't work at it, you won't be any better.

It doesn't seem like there's any way for the magical dilution thing to work without Muggle-borns being inherently weaker, which is obviously not canon, or, as I concluded when I so dismally tried to patch up the theory, all Muggle-borns being very bright, and intelligence being tied directly to magic. I'd like to agree with Aida on the part about magic-being a skill, though I would like much better a nice, clean explanation of magical genetics. *sigh* I guess that's not going to happen.

Originally Posted by AidaLuthien

Second, why would Native Americans be unaware of what magic meant? Just because they do not have a history of discriminating against witches doesn't mean that they wouldn't be able to figure out when someone can do things like not be injured when they're dropped out a window (see: Neville)

This is a discussion for the New World Natives thread, but in brief, I simply mean that I expect Indians viewed magic radically differently from European wizards - they might not have considered it inborn to certain people, or even have viewed magical events as magical or caused by a person. So if little Indian Neville had fallen out of a window (or tree/off a cliff, as the case may be), they might have attributed his lack of injury to a god, spirit, magical object, or another person's magic. The specific examples I was thinking of were the Shawnee Prophet and Chief Crazy Horse. The Shawnee Prophet told his warriors that his magical protection failed at the Battle of Tippecanoe because his menstruating wife had touched his sacred objects, which was considered an acceptable explanation, though that obviously does not jive with JKR's wizards - leading me to believe in HP canon, the Prophet would not have been a wizard. Crazy Horse, on the other hand, was, according to legend, never injured by a gun until his death, despite being shot at quite a bit, which I like to imagine could mean he would be a wizard with the ability to unconsciously cast some sort of shield charm. But I really don't know a lot about Indian culture/traditions/history, so I could be wrong about everything. Still, there must be some society that didn't place a value on magical blood, so why isn't there an area out there that's entirely wizards? But then, maybe there is, just not the Native Americans.
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